Each entry in specification_list
points to a string in the format XrmPutLineResource. following a call
to XtAppSetFallbackResources, when a resource database is being created
for a particular screen and the Intrinsics are not able to find or read
an application-specific class resource file and if specification_list is
not NULL the resource specification in specification_list will be merged
into the screen resource database in place of the application-specific class
resource file. XtAppSetFallbackResources is not required to copy specification_list;
the caller must ensure that the contents of the list and the strings addressed
by the list remain valid until all displays are initialized or until XtAppSetFallbackResources
is called again. The value NULL for specification_list removes any previous
fallback resource specification for the application context. The intended
use for fallback resources is to provide a minimal number of resources
that will make the application usable (or at least terminate with helpful
diagnostic messages) when some problem exists in finding and loading the
application defaults file.